Distillation involves heating a liquid to create vapor, which is collected when condensed at a separate location from the original liquid, based on the different boiling points or volatilities of the components of the liquid. To effectively accomplish multicomponent separation using distillation, it is necessary to accurately identify the various factions as they are condensed.
Presently, determination of fraction points of a distillation includes measurement of the system temperature and pressure, knowledge of the boiling points of the desired products, and observing changes in color of the receiver. Typically, higher boiling point products exhibit darker color than lower boiling point products; therefore, the color of the received products darkens as the distillation temperature increases. However, the varying rates of products moving through the system may result in multiple fractions having different boiling points being grouped together, making the exact points of separation difficult to determine.
Additionally, if the boiling points of the desired products are close, these products will boil and condense at the same time, requiring additional distillations to achieve the required purity. Therefore, it is necessary to carefully control the distillation system throughout the separation process.